The present invention relates generally to the field of automatic transmission systems and, more particularly, to a replacement intermediate shaft assembly for the Chrysler A518 and A618 and other similar transmissions.
The intermediate shaft assembly in the aforementioned Chrysler A518 and A618 transmissions (hereinafter “transmissions”) is located within and extends through the aft transmission housing and overdrive piston retainer mounted thereon and functions generally to interconnect the reverse drum component within the transmission housing to the overdrive assembly attached to the exterior of the housing. The intermediate shaft assembly including the structural features thereof also comprises an integral portion of the transmission lubrication circuit as hereinafter explained.
The original equipment manufacture (hereinafter “OEM) intermediate shaft assembly of the Chrysler transmissions is susceptible to premature wear on its integral bearing surfaces and external splines, and delivers inadequate lubrication to the front planetary gears, the overdrive planetary gears, and to the overdrive support causing premature wear of many surrounding parts. This is due primarily to the design of the automatic transmission fluid (hereinafter “ATF”) inlets within the OEM intermediate shaft, which fails to provide a sufficient flow of ATF to the aforementioned components under normal operating conditions.
Another recurring problem in the OEM intermediate shaft is stress cracking and eventual breakage of the shaft, which typically occurs at the rearward end thereof in proximity to the spline relief grooves machined adjacent the external spline formed on the shaft. The OEM intermediate shafts are also internally drilled to distribute lubrication to the various planetary gears and bearings throughout the transmission. Any such discontinuity in a machine part alters the stress distribution in the area of the discontinuity. Such discontinuities are called stress raisers, and the regions in which they occur are called areas of stress concentration.
The mechanical stresses imposed on the OEM intermediate shaft during peak torque events can produce stress cracks within such spline relief grooves due to their configuration and proximity to the internal lubrication passages drilled in the shaft. Once a crack is initiated, the stress concentration effect becomes greater and the crack progresses more rapidly. As the stressed area decreases in size, the stress increases in magnitude until the remaining area suddenly fails.
Thus, the present invention has been developed to resolve this problem by providing a direct replacement intermediate shaft assembly for the Chrysler transmissions, which provides improved ATF flow within the shaft and delivers a sufficient flow of lubrication to the front planetary gears, the overdrive planetary gears, and other components served by the shaft lubrication circuit. The present intermediate shaft also provides spline relief grooves and bearing journal relief grooves which are semicircular in cross-section to reduce areas of stress concentration.